Adhesive contamination-control mats of various sizes, configurations, materials, and constructions have been produced for many years. These products serve two primary functions: (1) To reduce contamination traceable to dirt carried by shoes and wheels by seizing the dirt and containing it on an adhesive surface; (2) to reduce the amount of shoe and heel carried dirt that might be converted into atmospheric dust (micro-particulate matter) if not stopped and contained on the adhesive surface. Reduction of dirt on shoes, wheels, and in the air results in the reduction of potentially dangerous bacteria and thus may serve to reduce infections in patients in surgical operating rooms and other critical patient care areas. Reduction of such dust also reduces failure of electronic parts and improves laboratory processes where dust contamination control is vital.
The incidence of hospital bacterial contamination has been one of increasing frequency and fact. The growing number of areas called Clean Rooms installed by laboratories and industry to help control atmospheric microparticulate contamination is well recognized and has created a new phase of laboratory design over the past twenty years. At this writing, annual sales of adhesive-coated contamination-control mats exceeds $20,000,000.00 The various early designs of such adhesive mats have evolved down to two basic product constructions: a thick, approximately one-quarter inch thick single-layer mat made of a soft polyvinyl chloride material and a multi-layer, stack of adhesive-coated plastic films.
Single-layer mats have the advantage that the weight and inertia of the mat enables it to lie flat on the floor surface without any specific added means of floor adhesion. Also, the surface has a very low level of adhesiveness, yet its soft upper-facing surface does tend to remove dust and dirt from shoes and wheels crossing across its surface. The product, therefore, has the advantage of being both effective and comfortable to walk upon and to stand upon. Its adhesive level is not apparent to the user; it does not pull on the shoe. However, when the surface becomes dirtied, it quickly becomes ineffective. Then the dirt must be removed by a water washing process and the surface dried with a lint-free towel before the product is again ready for use. Over a period of many such washings, the surface becomes scratched and pitted and as a result loses much of its effectiveness, because of the continual wearing process. Another negative factor is that the product has a high profile due to is thickness of approximately one-quarter inch, thus creating a trip hazard. Mainly because of high initial cost to the buyer, the gradual loss of function, and the high labor cost of continual constant rewashing, the market penetration of the simple-layer mat has been limited.
Multi-layer mats, comprise a stack or lamination of, presently, up to about thirty layers of pressure-sensitive adhesive-coated plastic films with the adhesive coat facing upward. The adhesive surface removes dirt and dust from shoes and wheels. When its surface is dirty, and therefore loses its effectiveness, the top sheet is removed from the stack and discarded, revealing another clean sticky surface, ready for use. No washing is required or attempted; so no degradation of surface of the type encountered by single-layer mats occurs, for there is no long term wear since each sheet is removed and discarded when dirty. Hence, this construction has attained the major market share. However, it has a high cost of daily usage. The two major producers of the stack concept product use an adhesiveness level which is very high as compared to the single layer product previously described, and as a result these products are uncomfortable to stand upon. Shoes get stuck and have sometimes been pulled off. The user therefore tends to walk across the surface as quickly as he can, if it is not possible to avoid walking over the mat. The highly aggressive tack level and the high cost of usage generally restricts the product to small entrance areas only.
These prior-art laminated stacks have been constructed of adhesive-coated low-density polyethylene films, each layer being approximately 2.5 mils in thickness or greater, plus an upward facing pressure-sensitive adhesive layer of approximately 0.333 mils. The product of one major producer, a thirty layer stack, is about ninety-four mils thick. The stack is held to the floor by means of a pressure-sensitive adhesive coating on the downward facing bottom layer. The thickness of these products creates a problem of edge height resulting in possible tripping of the user or scuffing of the product's edges. One producer helps to solve this height problem by mechanically bevelling the edge. The other producer does not bevel the edge but instead emphasizes the edge by placing the product in a rigid frame which is secured to the floor.
A major problem with current multi-layer stacks is the danger of premature sheet-to-sheet delamination. A clean rubber-soled shoe, typical of those used in hospitals, worn by a person weighing 150 pounds and pressed to an adhesive surface of ten ounces of adhesion (method 2050 or FTM STD NO-101 B) will develop 320 ounces of direct upward pull. This upward pull tends to pull the sheet loose from the underlying layer and to wrap around the shoe or wheel, thereby resulting in potential danger to the user. One company helps to solve this problem by providing a tiny dry-stripe non-adhesive coated edge on the edges of each sheet. Therefore a clean shoe sole does not come into contact with adhesive at the edge of the adhesive-coated sheet or layer where the danger of delamination is greatest. The other major producer uses its floor frame to good advantage. The edge of the frame being higher than the edge of the floor mat, the shoe of the user cannot come into contact with the extreme edge and, thereby, helps prevent delamination.
Current adhesive-coated contamination control plastic film mats are constructed of low-density polyethylene film at least 2.5 mils thick. The tensile strength of uncoated low-density polyethylene is generally 2800 p.s.i. Low-density polyethylene film can be made more resilient or stretchy by the addition of small percentages of other chemicals such as polyvinyl chloride. When such a sheet of plastic film is adhered to an adhesive-coated film which has an adhesion of eight to ten ounces of pull or adhesion per inch of width, the film must be strong enough to withstand the pull load of removal without tearing or shredding. This requisite strength has heretofore been accomplished via film thickness. A one-mil low-density polyethylene film would often tear upon removal from a ten-ounce adhesive-coated substrate.
With both concepts of the tacky mat product, the multi-layer stack and the washable single-sheet, the dirt and bacteria remain adhered to the sticky surface until either peeled off (as with the stack product) or washed (as with the single-layer washable product). One producer has incorporated an anti-bacterial chemical into its adhesive which, it claims, helps to kill the bacteria while they are held in place on the contamination control mat.